Many electronic color separation scanners are currently on the market. Conventional scanners suffer from the disadvantage that they are relatively difficult to operate, particularly because the operator is repeatedly confronted with a wide variety of possible courses of actions, some of which may be incompatible relative to previously selected courses of action.
For example, a user prescans an image, using an electronic color separation scanner such as the Smart Scanner, commercially available from Scitex Corporation, Herzlia, Isreal. The prescanned image is displayed to the user who selects a point in the prescanned image to serve as a white point. The selected point is then transformed to "absolute white". The user then corrects the color cast of the highlights. For example, the user may think that the light grays have a yellow cast, i e., are too yellow and make an appropriate correction. However, this correction affects his previous selection of the white point by reducing the yellow component of the white point, thereby giving a bluish tone to the absolute white locations of the picture.
Another example is that a user may first increase the brightness level of a color image. The user subsequently selects a relatively non-bright point as the white point because the selected relatively non-bright point, according to the context of the picture, should be white. This operation results in brightening of all points somewhat less bright than the selected point which causes the entire picture to appear too bright.